7 The 100 Most Influential Inventors of All Time 7

Guglielmo Marconi, c. 1908. Library

of Congress, Washington, D.C.

Other Inventions

In 1920 De Forest began to work on a practical system for

recording and reproducing sound motion pictures. He

developed a sound-on-fi lm optical recording system called

Phonofi lm and demonstrated it in theatres between 1923

and 1927. Although it was basically correct in principle, its

operating quality was poor, and he found himself unable to

interest fi lm producers in its possibilities. Ironically, within

a few years’ time the motion-picture industry converted

to talking pictures by using a sound-on-fi lm process similar

to De Forest’s. During the 1930s De Forest developed

Audion-diathermy machines for medical applications, and

during World War II he

conducted military

research for Bell

Laboratories.

Guglielmo Marconi

(b. April 25, 1874, Bologna,

Italy—d. July 20, 1937, Rome

I

talian physicist

Guglielmo Marconi

was the inventor of a

successful wireless tele-

graph (1896). In 1909 he

received the Nobel Prize

for Physics, which he

shared with German

physicist Ferdinand

Braun. He later worked

on the development of